Transmission Synthetic Oil

[livehho]

Any real advantage in using full synthetic in the Manual Transmission? Right now using dino SAE 80W-90 API GL-4. I'm going to repack the trans tomorrow so wanted to know if it's worth it to switch to synth. cool. Also, any damage if switching for GL-5?

 

[sciphi]

Get some Redline MT-90 and call it a day. If there's any notchiness the Redline may smooth it out. That happened on my last car.

 

[mechtech2]

A trans shears/cuts lube pretty well. I'd go with a synthetic.
But it's not necessary.
For instance, there are Synchromesh fluids that are great, and they are dino.
If you change the transmission fluid every 2-3 years, a modern full synthetic from Redline or Amsoil will give the best protection, and importantly, shifting.

 

[tig1]

Synt. transmission oil has worked well for me for many years. Amoung it's benefits are longer OCI, lower transmission temps, less wear.

 

[artificialist]

You can use a GL4/GL5 gear oil but it will not be ideal, because GL5 oils have more sulfur than what is ideal in a manual transmssion.

Amsoil and Red Line make special GL4 only synthetic fluids.

 

[hsd]

I switched to RL MT-90 in my 280ZX 5 speed and it works much nicer than the standard lube.

 

[m37charlie]

The decision making re a synthetic trans oil is like for a motor oil.
Do you live in an area with extreme low temps (definitely NO) or does the transmission get very hot?
Are you planning on very extended drain intervals? Synthetic oils like
http://www.mobil.com/USA-English/Lubes/P...on_Fluid_50.asp
are rated for 500K miles in heavy trucks that pile up mileage.
If any answers are yes, use a high quality synthetic.
Otherwise, no.
Be sure the oil is GL4 or GL4/GL5 rated, not just GL5, if the transmission has bronze synchros.

Charlie

 

[ediamiam]

Originally Posted By: sciphi
Get some Redline MT-90 and call it a day. If there's any notchiness the Redline may smooth it out. That happened on my last car.

I concur

 

[mechtech2]

Also consider that the best and most appropriate manual trans lubes are fully synthetic.
What's a possible $5-10 more for a change every couple of years?